Photographic elements, compositions and processes

ABSTRACT

N-hydroxyurea silver halide developing agents in photographic processing compositions, elements and processes provide desired developing activity. These can be employed in various photographic products including processing compositions, photosensitive compositions, photographic elements and chemical transfer systems. They can be used in combination with other silver halide developing agents and with addenda commonly employed in photographic processing compositions and elements.

Wilson et al.

PHOTOGRAPHIC ELEMENTS, COMPOSITIONS AND PROCESSES Inventors: Burton D.Wilson; Paul E.

Woodgate, both of Rochester; Richard W. Henn, Pittsford, all of NY.

Eastman Kodak Company, Rochester, NY.

Filed: June 13, 1974 Appl. No.: 479,024

Related US. Application Data Assignee:

[ June 3, 1975 2,404,774 7/1946 Dersch 96/66.3 2,477,323 7/1949 Wood96/66.3

2,819,165 1/1958 Mackey 96/61 3,438,776 4/1969 Yudelson 96/66 R3,730,727 5/1973 Olivares et al.... 96/95 3,794,488 2/1974 Henn et al.96/50 R Primary ExaminerMary F. Kelley Attorney, Agent, or FirmR. E.Knapp [5 7] ABSTRACT N-hydroxyurea silver halide developing agents inphotographic processing compositions, elements and processesprovidedesired developing activity. These can be employed in variousphotographic products including processing compositions, photosensitivecompositions, photographic elements and chemical transfer systems. Theycan be used in combination with other silver halide developing agentsand with addenda commonly employed in photographic processingcompositions and elements.

4 Claims, No Drawings 1 PHOTOGRAPHIC ELEMENTS, COMPOSITIONS ANDPROCESSES This is a divisional of U.S. Pat. application Ser. No. 252,036of Wilson, Woodgate and Henn, filed May 10, 1972 now abandoned as theupdated status of Ser. No. 252,036.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to N-hydroxyurea reducing agents in photographic elements,compositions and processes. In one of its aspects it relates tophotographic processing compositions containing these N- hydroxyureareducing agents. In another aspect it relates to photographic elementscontaining such reducing agents. In a further aspect it relates tophotographic compositions and to processes, such as processing withheat, to develop an image in a photographic element.

2. Description of the State of the Art The use of various nitrogencontaining compounds as photographic developing agents and for otherpurposes in photographic materials is known. For example, hydroxylamineshave been used as developing agents as described, for example, inBelgian Pat. No. 558,501 of Gevaert published July 15, 1957; U.S. Pat.No. 3,287,125 of Green et al., issued Nov. 22, 1966 and the like.Certain urea derivatives have also been employed in photographicmaterials as described in Canadian Pat. No. 456,029 and U.S. Pat.2,404,774 of Derisch et al., U.S. Pat. No. 2,477,323 of Wood issued July26, 1949 and U.S. Pat. No. 2,819,165 of Mackey, issued Jan. 7, 1958.Hydroxymethylurea compounds have also been employed in diazo materialsas described in U.S. Pat. 3,453,112 of Schaefer, issued July 1, 1969;U.S. Pat. No. 3,316,092 of Klimkowski et al. issued Apr. 25, 1967 andFrench patent of addition No. 83,978 of Bauchet published Sept. 28,1964. However, these are not N-hydroxyurea reducing agents of theinvention. There has been a continuing need to provide nitrogencontaining reducing agents for photosensitive materials which providereduced staining propensity. While hydroxylamine and various derivativeshave been employed for this purpose, they have not always providedsufficient developing activity or stability. This is demonstrated infollowing comparative Example 9.

There has also been a continuing need to provide combinations ofreducing agents which provide reduced processing time and reducedstaining propensity. This is especially important in photosensitivematerials for processing with heat in which the processing agents remainin the photosensitive material after processing.

Accordingly, it is an object of the invention to provide photographicelements, processing compositions, photosensitive compositions andprocesses, such as photographic materials for processing with heat,employ certain silver halide developing agents which provide decreasedprocessing time with reduced staining propensity.

SUMMARY OF THE INVENTION According to the invention decreased processingtime with reduced staining propensity, without significant loss ofdesired sensitometric properties, is provided in a photographic element,composition, processing composition and/or process by an N-hydroxyureasilver halide developing agent. Such N-hydroxyurea silver halidedeveloping agents provide especially suitable results when employed incombination with other silver halide developing agents, such as3-pyrazolidone silver halide developing agents.

The described N-hydroxyurea silver halide developing agents are suitablein photothermographic materials containing a photosensitive componentwith an oxidation-reduction imageforming combination.

The N-hydroxyurea silver halide developing agents described yieldcolorless oxidation products which are especially suitable inphotosensitive materials which require that the processing agents remainin the photosensitive material after processing. The N-hydroxyureadeveloping agents provide surprisingly reduced propensity for stainingcompared to prior art silver halide developing agents such ashydroquinone and paraaminophenol silver halide developing agents whichprovide undesired oxidation stain. This is demonstrated in followingcomparative Example 17.

DETAILED DESCRIPTION OF THE INVENTION A variety of N-hydroxyureareducing agents can be employed according to the invention. One test forsuitable N-hydroxyurea reducing agents according to the invention whenthe reducing agents are to be employed in an aqueous alkaline processingcomposition is set out in following Example 1. A further test forsuitable N-hydroxyurea reducing agents when the reducing agent is to beemployed in a photothermographic material is set out in followingExample 18.

A useful class of N-hydroxyurea silver halide developing agentsaccording to the invention is represented by the formula:

R1 o R r II 1 N c N I R2 on wherein R, R and R are hydrogen, alkyl,especially alkyl containing 1 to 4 carbon atoms, such as methyl, ethyl,propyl and butyl, or aryl, typically aryl containing 6 to 10 carbonatoms, such -as phenyl, tolyl and xylyl. R R and/or R can containsubstituent groups which do not adversely affect developing activity ofthe described N-hydroxyurea silver halide developing agents. Suchsubstituent groups include, for example, halogen or amino groups. Withinthe described class of N-hydroxyurea silver halide developing agentsespecially useful reducing agents are those wherein R is hydrogen, alkylcontaining 1 to 4 carbon atoms or aryl containing 6 to 10 carbon atoms,such as phenyl, tolyl or xylyl; R is hydrogen, alkyl of l to 4 carbonatoms or aryl containing 6 to 10 carbon atoms such as phenyl, tolyl orxylyl; R is hydrogen, alkyl containing 1 to 4 carbon atoms or phenyl,tolyl or xylyl. Examples of suitable N-hydroxyurea silver halidedeveloping agents are compounds wherein R, R and R in the describedstructure are as follows:

-Continued Compound No.

As can be seen from Examples 2, 3, 4 and 5, above, preferredN-hydroxyurea silver halide developing agents can be represented by theformula methoxyphenyl or p-chlorophenyl.

The described N-hydroxyurea reducing agents can be prepared byprocedures known in the art.

The described N-hydroxyurea reducing agents can be employed in a rangeof physical locations in a photographic system. They can be employed inone or more layers of a photographic element and/or in a processingcomposition if desired. The optimum location will depend upon thedesired image, processing conditions, particular photographic system andthe like. For example, the described N-hydroxyurea silver halidedeveloping agents can be employed in a processing composition, such asan aqueous, alkaline developer solution or they can be incorporated intoone or more layers of a photographic element, such as a photographicsilver halide emulsion layer, a layer between the support and aphotographic silver halide emulsion layer, and/or an overcoat layer.

One embodiment of the invention is a photographic processing compositioncomprising an alkaline devel' oper activator and an N-hydroxyurea silverhalide developing agent, as described. This is typically an aqueousalkaline solution.

Various development activators can be employed in the practice of theinvention. These include any of those which provide the desiredactivation of the described developing agents. These include, forinstance, alkaline development activators, such as inorganic alkaliesincluding, for example, sodium hydroxide, potassium hydroxide and/orlithium hydroxide, alkali metal carbonates such as sodium carbonate, andpotassium carbonate, alkali metal phosphates such as trisodiumphosphate, and/or organic alkaline development activators such asquaternary ammonium bases, amines such as amino alkanols and similaralkaline materials and/or alkali releasing materials. The describeddevelopment activators can be employed in the described processingcomposition and/or applied to the described photographic element in anysuitable manner including, for example, dipping, spraying and/orsuitable surface applications such as with rollers or other mechanicalmeans.

The pH of the processing composition should be sufficient to providedesired activation of the described developing agent. A pH of about toabout 14 is typically employed.

A wide range of concentration of the described developing agent can beemployed in a processing composition in the practice of the inventiondepending upon the desired image, the developing agent employed,processing conditions and the like. A concentration of about 0.5 toabout 50 grams, and typically about 2 to about 20 grams of developingagent is suitable per liter of processing composition.

The described silver halide developing agents can be employed incombination with any silver halide developing agent or developing agentprecursor which does not adversely affect the developing activity of theN- hydroxyurea compounds. Suitable silver halide developing agents whichcan be employed include, for example, polyhydroxybenzenes, such ashydroquinone silver halide developing agents, such as hydroquinone,alkylsubstituted hydroquinones, as exemplified by tertiary butylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and2,6-dimethylhydroquinone; catechols and pyrogallol; chlorosubstitutedhydroquinones, such as chlorohydroquinone or dichlorohydroquinone;alkoxy substituted hydroquinones such as methoxy hydroquinone or ethoxyhydroquinone; aminophenol developing agents such as 2,4- diaminophenolsand methylaminophenols; ascorbic acid developing agents such as ascorbicacid, ascorbic acid ketals and ascorbic acid derivatives; hydroxylaminedeveloping agents such as N,N-di(2- ethoxyethyl) 3-pyrazolidonedeveloping agents such as 1-phenyl-3'pyrazolidone and/or 4-methyl-4-hydroxymethyl-l-phenyl-3-pyrazolidone; and the like. Combinations ofthese developing agents can be employed if desired.

The combination of the described N-hydroxyurea silver halide developingagents with a 3-pyrazolidone developing agent provides surprisinglyreduced processing time to provide desired image density withoutundesired increase in minimum density. Typical 3- pyrazolidone silverhalide developing agents which can be employed in this combination aredescribed, for example, in US. Pat. No. 3,453,109 of Lee issued July 1,1969; US. Pat. No. 3,284,200 of Ficken issued Nov. 8, 1966; U.S. Pat.3,523,795 of Ohkubo et al issued Aug. 11, 1970; British Pat. No.1,093,281 issued Nov. 29, 1967 and US. Pat. No. 2,875,048 of Haist andKing issued Feb. 24, l959. Typical 3-pyrazolidone silver halidedeveloping agents which can be employed in the described combinationinclude, for example, l-phenyl- 4,4-dihydroxymethyl-3-pyrazolidone;1-phenyl-4- methyl4-hydroxymethyl3-pyrazolidone; l-phenyl-3-pyrazolidone; 5-phenyl-3-pyrazolidone; 5-methyl-3- pyrazolidone and thelike.

A range of concentrations of the described N- hydroxyurea silver halidedeveloping agent can be employed with a range of concentrations of thedescribed 3-pyrazolidone silver halide developing agents. Typically aconcentration ratio of 10 parts by weight N- hydroxyurea silver halidedeveloping agent is employed for each part by weight of 3-pyrazolidonesilver halide developing agent. A typical concentration range of 3-pyrazolidone silver halide developing agent in a processing compositionis about 0.05 grams to about 5 grams of 3-pyrazolidone silver halidedeveloping agent per liter of processing composition.

The described silver halide developing agents can be employed in a rangeof photographic processing compositions, such as in photographic silverhalide developer compositions, hardener compositions, monobaths, and thelike.

The photographic processing composition can contain a silver halidesolvent if desired. Typical silver halide solvents include, for example,alkali metal or ammonium thiosulfates and thiocyanates, such as sodiumthiosulfate, sodium thiocyanate or ammonium thiocyanate and organicsilver halide solvents such as thiourea and certain organic amines.

The processing composition as described can be a monobath. Typicalcomponents of monobaths are described, for example, in the MonobathManual by Grant and Haist, published by London Press, 1966.

Another embodiment of the invention is a photosensitive compositioncomprising a photosensitive component, especially a photosensitivesilver salt, and an N- hydroxyurea silver halide developing agent asdescribed. The photosensitive silver salt is typically a photosensitivesilver halide.

A range of concentration of the described N- hydroxyurea silver halidedeveloping agent can be employed when the developing agent is acomponent of a photographic element and/or photosensitive compositionsuch as a photosensitive silver halide emulsion. Typically theconcentration of silver halide developing agent is about 0.1 mole toabout 50 moles of developing agent per mole of silver present in thephotographic element or photosensitive composition, preferably about 05moles to about 4 moles of silver halide developing agent per mole ofsilver in the element or composition. This typically corresponds toabout to about 500 milligrams of silver halide developing agent per 929square centimeters of support. When used in photosensitive materials forprocessing with heat typically a concentration of about 0.1 to about 2moles of N- hydroxyurea developing agent is employed per mole of silverin the photosensitive material.

Silver halide materials which can be employed according to the inventioninclude any photosensitive silver halide, such as silver chloride,silver bromide, silver bromoiodide, silver chlorobromoiodide or mixturesthereof. The silver halide materials which are suitable are described inthe Product Licensing Index, Volume 92, December, 1971, publication9232, pages 107-110 in paragraphs I, II and III. A photosensitive silverhalide can be chemically sensitized as described in paragraph 111 ofthis Product Licensing Index Publication.

The silver halide photosensitive elements and compositions according tothe invention can contain development modifiers, antifoggants,stabilizers, hardeners, plasticizers and lubricants, coating aids,matting agents, brighteners and spectral sensitizing dyes described inthe Product Licensing Index, Vol. 92, December, 1971, publication 9232,pages 107-1 10. The silver halide photosensitive compositions accordingto the invention can be chemically sensitized, washed and/or coatedemploying the procedures described in this publication.

Another embodiment of the invention accordingly is a photosensitivesilver halide emulsion comprising photosensitive silver halide, a binderand an N hydroxyurea silver halide developing agent as described.

A photographic element and/or composition described according to theinvention can contain various colloids alone or in combination asvehicles, binding agents and in various layers. Typically hydrophilicmaterials are employed in those instances where aqueous solutions are tobe used in processing. However, in those instances in which thephotosensitive material is for processing with heat, a hydrophobicbinder can be used. Accordingly, hydrophilic and/or hydrophobicmaterials can be employed as binders depending on the particularphotosensitive material and the intended processing. Suitablehydrophilic materials include naturally-occurring substances such asproteins, for example, gelatin, gelatin derivatives, cellulosederivatives, polysaccharides such as dextran, gum arabic and the like;and synthetic polymeric substances such as water soluble polyvinylcompounds like poly(vinylpyrrolidone), acrylic polymers and the like.Other synthetic polymeric compounds which can be employed includedispersed vinyl compounds such as in latex form and particularly thosewhich increased dimensional stability of photographic materials.Suitable synthetic polymers include those described in the ProductLicensing Index, Volume 92, December, 1971, publication 9232, pages107-110 in paragraph VIII.

The photosensitive materials and other layers of a photographic elementaccording to the invention can be coated on a wide variety of supports.Typical supports include cellulose nitrate film, cellulose ester film,poly(vinyl acetal) film, polystyrene film, polyethylene terephthalate,film, polycarbonate film and related films or resinous materials as wellas glass, paper, metal and the like. Typically a flexible support isemployed, especially a paper support which can be partially acetylatedor coated with baryta and/or an alpha olefin polymer particularly apolymer of an alpha olefin containing 2 to 10 carbon atoms such aspolyethylene, polypropylene, ethylene-butene copolymers and the like.

Another embodiment of the invention is a photographic element comprisinga support having thereon a photosensitive silver salt, typicallyphotosensitive silver halide, an N-hydroxyurea silver halide developingagent, as described, and a binder.

The photosensitive silver halide materials employed according to theinvention can be x-ray or other nonspectrally sensitized materials orthey can contain spectral sensitizing dyes as described.

The sensitizing dyes and/or other addenda, such as the described silverhalide developing agents according to the invention, can be added fromwater solutions or suitable organic solvent solutions can be used. Thecompounds can be added using various procedures known in thephotographic art as described in the mentioned Product Licensing Indexpublication.

The described N-hydroxyurea silver halide developing agents can beemployed in combination with a socalled stabilizer precursor. These aretypically sulfurcontaining compounds contiguous to photographic silverhalide which in the presence of an activator breakdown or cleave to forma compound that combines or complexes with the silver halide inunexposed and undeveloped areas of a photographic element to form acomplex or compound which is believed to be a silver mercaptide which ismore stable than silver halide to light humidity and ambient conditions.Such compounds are described, for example, in US. Pat. No. 3,301,678 ofHumphlett et 211, issued Jan. 31, 1967; Belgian Pat. No. 709,967 andBelgian Pat. 709,900. Examples of suitable silver halide stabilizerprecursors include 3-S-isothiuronium propane sulfonate; 2-S-isothiuronium ethane sulfonate and 1,8-(3,6- dioxaoctane)bis(isothiuronium trichloroacetate). A

suitable concentration of stabilizer precursor will vary depending onthe particular photographic element, the desired image, processingconditions and the like. Usu' ally a concentration of about 0.25 toabout 10 molels of stabilizer precursor per mole of photosensitivesilver halide in the element is suitable.

After exposure, the resulting latent image in a photographic elementcontaining the described silver halide developing agent can be developedby contacting the element with an alkaline development activator asdescribed. An especially suitable activator is an alkaline aqueoussolution containing an alkali metal hydroxide at a pH of about 10 toabout 14.5, especially 12 to 14.5. The described development activatorscan be applied to the photographic element according to the invention inany suitable manner which provides desired activation including, forexample, dipping, spraying, and/or surface application such as withrollers or by surface application processing.

So-called web processing can be employed as described, for example, inUS. Pat. No. 3,179,517 ofTregillus et al., issued Apr. 20, 1965 orso-called stabilization processing as described in Russell et al, PSAJournal, Volume 16B, August, 1950.

The time for processing a photographic element containing a developingagent according to the invention, that is developing a desired latentimage, can vary over a wide range, typically between about 1 second toseveral minutes depending on the desired image, processing conditions,particular developing agent and the like.

Processing conditions can also vary. When the described developing agentis in a processing solution and/or in a photographic element, processingis usually carried out under ambient pressures and temperatures of about20C. to about 30C. If desired, higher temper atures can be used.

The described N-hydroxyurea silver halide developing agents can beemployed in a diffusion transfer photographic system, especially aphotographic silver salt diffusion transfer system. The describeddeveloping agents can be employed in one or more layers of aphotographic element and/or in a processing composition in such a systemif desired. Suitable diffusion transfer systems, processes, processingcompositions and elements therefore are described, for example, in U.S.Pat. No. 2,452,181 of Land issued Feb. 27, 1951; and US. Pat. 3,337,342of Green issued Aug. 27, 1967. Accordingly, another embodiment of theinvention is: in a photographic product comprising in combination (a) aphotographic element comprising photographic silver halide, (b) aprocessing composition containing a silver halide solvent, and (c) animage-receiving layer an N- hydroxyurea silver halide developing agentas described. The N-hydroxyurea silver halide developing agent istypically present in the processing composition. The product istypically employed for developing an image by exposing the photographicsilver halide element to form a latent image therein; developing thelatent image with a processing composition, such as at a pH of about 12to about 14, containing the described N-hydroxyurea silver halidedeveloping agent with a silver halide solvent; contacting undevelopedsilver halide in the photographic silver halide layer with the silverhalide solvent to form an imagewise distribution of a silver complex inthe unexposed areas of the photo graphic silver halide layer;transferring at least part of the silver complex to an image receiverlayer contiguous to the photographic silver halide layer; reducing thesilver complex in the presence of development nuclei to form a visibleimage in the receiver layer; and lowering the pH of the processingcomposition to below about 8 to form a stable developed image.

The developing agents according to the invention can be present in oneor more layers of elements designed for color photography, for example,elements containing color-forming couplers, or elements to be developedin solutions containing color-forming couplers; or in so-calledfalse-sensitized color materials such as those described in US. Pat. No.2,763,549 of Hanson issued Sept. 18, 1956.

If desired, the developing agents can be employed in so-called hardeningdevelopers such as described in US. Pat. No. 3,232,761 of Allen andBurness, issued Feb. 1, 1966; or in roller transport processors which isdescribed in US. Pat. No. 3,025,779 of Russell et al, issued March 20,1962.

The described developing agents can also be employed in photosensitivematerials designed for pro cessing with heat. Photosensitive materialsfor processing with heat in which the described N-hydroxyurea silverhalide developing agents are especially suitable are described, forexample, in US. Pat. No. 3,457,075 of Morgan et al, issued July 22,1969; US. Pat. No. 3,152,904 of Sorenson et al., issued Oct. 13, 1964;US. Pat. No. 3,392,020 of Yutzy et al., issued July 9, 1968; and BelgianPat. No. 705,872. In photosensitive elements for processing with heattypically a support is provided having thereon an oxidationreductionimage forming combination comprising an oxidizing agent, typically aheavy metal salt oxidizing agent, such as a silver salt of a fatty acid.with an N-hydroxyurea reducing agent and a catalyst for theimage-forming combination, such as photosensitive silver halide. Avisible image is produced after exposure of the photosensitive elementWithin a short time, such as about 1 to about 60 seconds, after exposureby heating the element to moderately elevated temperatures, such asabout C. to about C.

Accordingly, another embodiment of the invention in a photothermographicelement comprising a support having thereon a photosensitive component,such as a photosensitive silver salt, an oxidation-reductionimage-forming combination comprising (a) an oxidizing agent, typically aheavy metal salt oxidizing agent, such as silver behenate, with (b) anN-hydroxyurea reducing agent as described.

The described photosensitive component in this photothermographicmaterial is believed to function as a catalyst for the image-formingcombination. A typical concentration range of photosensitive component,especially photosensitive silver halide, in the describedphotothermographic element is from about 0.005 to about 0.50 moles ofphotosensitive silver salt per mole of oxidizing agent.

In photothermographic materials the described N- hydroxyurea reducingagents can be employed in combination with other described reducingagents, typically a substituted phenol and/or naphthol. For example, theN-hydroxyurea reducing agents can be employed in combination withbis-beta-naphthol reducing agents, such as2,2-dihydroxy-l,l'-binaphthol, 6,6'-dibromo-2,2'-dihydroxy-l,1-binaphthol, 6,6-dinitro-2,2-dihydroxy-1,1-binaphthol, or naphthol)methane.

The oxidizing agent in the described oxidationreduction image-formingcombination is typically a heavy metal salt oxidizing agent such as asilver salt oxidizing agent. The heavy metal salts of an organic acidare especially suitable, such as water insoluble silver salts oflong-chain fatty acids which are substantially stable to light.Compounds which are silver salts of long-chain fatty acids include, forexample, silver behenate, silver stearate, silver oleate, silverlaurate, silver hydroxystearate, silver caprate, silver myristate andsilver palmitate. Oxidizing agents which are not silver salts ofcarboxylic acids can be employed if desired such as silverphthalazinone, silver benzotirazole and- /or silver saccharin. Oxidizingagents which are not silver salts can be employed if desired such asgold stearate, mercuric behenate, auric behenate and the like, butsilver salts are preferred.

It is often desirable to employ a so-called activator toning agent inthe photothermographic elements and compositions according to theinvention in order to obtain improved tone and desired image density.The described activator toning agent is suitable in a range ofconcentration; however, it is especially suitable in a concentration ofabout 0.10 moles to about 1.1 moles of activator toning agent per moleof oxidizing agent employed such as per mole of silver behenate. Atypical activator toning agent which is suitable is a cyclic imide suchas phthalimide, N-hydroxyphthalimide, N- potassium phthalimide, N-silverphthalimide, N- mercury phthalimide, succinimide and/or N-hydroxysuccinimide. Other suitable activator toning agents include, forexample, phthalazinone, 2-acetyl phthalazinone and2-phthalylphthalazinone.

Binders can be employed in the described photothermographic materials asdescribed. Preferred binders are hgih molecular weight materials andresins including polyvinyl butyral, cellulose acetate butyrate,polymethylmethacrylate, poly(vinyl pyrrolidone), ethyl cellulose,polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene,butadiene styrene copolymers, vinyl chloride-vinyl acetate copolymers,copolymers of vinyl acetate, vinyl chloride and maleic acid andpolyvinyl alcohol.

If desired, the described photosensitive silver halide in thephotothermographic material according to the invention can be preparedin situ. A method of preparing photosensitive silver halide in situ in aphotothermographic material is described, for example, in U.S. Pat. No.3,457,075 of Morgan et a1. issued July 22, 1969.

Stability to print out from light exposure is increased in the describedphotothermographic materials typically by employing highly purifiedmaterials; for example, freedom from halides and sulfides increasesstability to light exposure. The use of highly purified silver behenatecan, for example, reduce propensity to print out in background areas ofa photothermographic element according to the invention.

In a developing image in a photothermographic material according to theinvention a range of processing temperatures is suitable. The processingtemperature range is typically about 80C. to about 250C. such as forabout 1 to about 60 seconds. By increasing or debis-( Z-hydroxylcreasing the length of time of heating, a higher or lower temperaturewithin the described range can be employed.

Any suitable means can be useful providing the desired processingtemperature range. The heating means can be a simple hot plate, rolleror the like.

In some cases, if desired, a photothermographic element can be preparedwherein one or more components such as the described photosensitivesilver halide can be in one layer and other components in other layers.For example, an element according to the invention can comprise asupport, a layer containing photographic silver halide and a layercomprising the socalled oxidation-reduction image-forming combinationcomprising a heavy metal salt oxidizing agent as described such assilver behenate with an N-hydroxyurea reducing agent as described.

A typical so-called oxidation-reduction imageforming combinationaccording to the invention comprises silver behenate with the describedN- hydroxyurea reducing agent and an activator toning agent which istypically phthalimide or phthalazinone.

Other addenda known to be useful in photosensitive and thermosensitiveelements as described in British Pat. No. 1,161,777 published Aug. 20,1969; U.S. Pat. No. 3,152,904 of Sorenson et a1, issued Oct. 13, 1964and U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22, 1969 canbe employed in photo-thermographic materials according to the invention.

The following examples are included for a further understanding of theinvention.

EXAMPLES 1-8 An N-hydroxyurea silver halide developing agent is mixed inan aqueous solution containing a 0.02 molar concentration of theN-hydroxyurea silver halide developing agent, a 0.2 molar concentrationof sodium sulfite and either a 0.2 molar concentration of sodiumphosphate with the pH adjusted to l 1.5 or a 0.5 molar concentration ofsodium hydroxide with the pH of the solution adjusted to approximately13.5. This provides a photosnsitive silver halide developer solution.

A photographic element containing a fine-grain silver bromoididegelatino emulsion on a film support is sensitometrically exposed througha step wedge to tungsten light. The photographic element contains about0.35 grams of silver per square foot of support. The resulting latentimage is developed-by immersing the film in the silver halide developersolution containing the N-hydroxyurea silver halide developing agent fora seris of times at 20C. Image densities of the resulting developedimage are observed. Image densities, time and fog density for eachN-hydroxyurea silver halide developing agent are listed in followingTable 1. Good image discrimination is obtained in each instance. Thecompound number in Table I and in the following examples corresponds tothe compound number of the N-hydroxyurea developing agent described.

Aqueous Development -Continued Aqueous Development pH pH 1 1.5 13.5

Mini- Mini- Com- Image mum Image mum Ex. pound Time Den- Den- Time Den-Den- No. No. (min) sity sity (min) sity sity EXAMPLE 9 This is acomparative example.

The procedure set out in Example 1 is repeated with the exception thathydroxylamine sulfate is employed in place of the describedN-hydroxyurea silver halide developing agent. The resulting image has adensity of 1.45 in 32 minutes at a pH of 11.5.

EXAMPLES 10-16 The procedure set out in Examples 1-5, 7 and 8 arerepeated with the exception that 0.002 molar concentration of1-phenyl-3-pyraz0lidone is added to the described developer solutions.Upon processing the results observed are set out in following Table II.

The combination of silver halide developing agents provide a developedimage in surprisingly reduced time and provide especially low minimumdensity compared to the results of Examples 18.

This example demonstrates reduced staining propensity of theN-hydroxyurea silver halide developing agents of the invention. 1-11 Analkaline solution of each of the N-hydroxyurea silver halide developingagents designated as compounds 1-1 1 are permitted to evaporate todryness in the presence of air. The residue in each instance is almostcolorless.

The procedure is repeated with the exception that hydroquinone isemployed in place of the N- hydroxyurea silver halide developing agent.The residue resulting upon evaporation is intensely colored.

This procedure is also repeated employing paraaminophenol in place ofthe described N-hydroxyurea silver halide developing agent. Uponevaporation the resulting residue is intensely colored. Thisdemonstrates that the N-hydroxyurea silver halide developing agents ofthe invention provide surprisingly reduced staining propensity comparedto silver halide developing agents employed herefore.

EXAMPLES 18-25 This illustrates the use of N-hydroxyurea silver halidedeveloping agents according to the invention in photosensitive materialsfor processing with heat.

A dispersion is prepared by mixing the following components:

Silveer behenate 23.3 g Behenic acid 26.0 g Polyvinyl butyral 1.25 gSodium bromide 1.31 g Acetone-toluene (1:1 parts by 500 ml volume) Thismixture is ball-milled for 18 hours and the resulting dispersion iscoated on a resin coated paper support at a wet thickness of 0.004inches. The resulting coating is permitted to dry under atmosphericconditions. Various N-hydroxyurea reducing agents as indicated infollowing Table III are each dissolved in a mixture of alcohol andacetone and coated on separate pieces of the resulting photosensitiveelement. The N- hydroxyurea silver halide developing agent is present ata concentration of 0.02 molar.

After the N-hydroxyurea reducing agent is introduced, the resultingphotothermographic element is dried and exposed sensitometrically tolight. The resulting image is developed by overall heating thephotothermographic element on a heated metal plate at C. Images ofmoderate to high density are produced within about 1 to 3 seconds asindicated in following Table lll. Good density corresponds to 0.8 max,Dense corresponds to 1.0 max., Fair corresponds to 0.5 "max.

This is a comparative example.

The procedure set out in Example 18 is repeated with the exception thathydroxylamine sulfate is employed in place of the describedN-hydroxyurea silver halide developing agent.

Upon exposure and overall heating, an image having almost no density isproduced. The image density is very poor compared to the image densityproduced in each instance in Examples 18-25.

EXAMPLES 27-34 The procedure set out in Examples 18-25 are repeated withthe exception that phthalazinone in a concentration of 0.7 g/g Ag. isemployed in the photothermographic elements described. In each instanceupon exposure and overall heating an image is developed within about 2to 4 seconds at a processing temperature of about 140C.

EXAMPLES 3541 Table IV Ex- Comample poun Temp Time Image Minimum ImageNo. No. "C (sec) Density Density Tone 35 2 15 1 High High 1 15 36 3 l 153 High Low Neutral 37 4 1 l5 1 High Low Neutral 38 5 90 9 Good LowNeutral 39 6 l 15 High Low Neutral 40 8 l 15 2 Good Low Neutral 41 9 1l5 7 Fair Low Neutral EXAMPLES 42-47 A photosensitive silver chloridegelatino emulsion is prepared containing 2.6 kilograms of gelatin and 2moles of silver chloride. The silver chloride gelatino emulsion is mixedwith 600 grams of gelatin, a wetting agent and one of the N-hydroxyureasilver halide developing agents as set out in following Table V. Aconcentration of 3.0 moles of N-hydroxyurea silver halide developingagent per mole of silver in the silver chloride gelatino emulsion isused.

The resulting silver chloride emulsion containing the N-hydroxyureasilver halide developing agent is coated on a paper support at aconcentration of 0.04 grams of silver per square foot of support. Afterdrying, the photographic element is sensitometrically exposed totungsten light. The resulting image is developed by immersing thephotographic element in an aqueous sodium hydroxide solution containing2.0 percent by weight sodium hydroxide for 5 seconds. An image isdeveloped in each instance as set out in following Table V. In eachinstance very good image discrimination is produced.

Table V Incorporation in Silver Halide Photosensitive Emulsion Theprocedure set out in Example 42 is repeated with the exeption that aftersensitometric exposure the photographic element is heated for 10 secondsat 200C. A developed image is produced having moderate image density.

EXAMPLE 49 graphic element is heated for 10 seconds at 200C. An

image is developed having moderate density.

EXAMPLE 50 The procedure set out in Example 47 is repeated with theexception that after imagewise exposure the photographic element isheated for 10 seconds at 200C. A developed image results having moderateimage density.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What is claimed is:

l. A photographic processing composition comprising an alkalinedevelopment activator and an N- hydroxyurea silver halide developingagent, said N- hydroxyurea silver halide developing agent beingrepresented by the formula:

wherein R is hydrogen, alkyl containing 1 to 4 carbon atoms or arylcontaining 6 to 10 carbon atoms; R is hydrogen, alkyl containing 1 to 4carbon atoms or aryl containing 6 to 10 carbon atoms; R is hydrogen,alkyl containing 1 to 4 carbon atoms or aryl containing 6 to 10 carbonatoms.

2. The photographic processing composition of claim 1 wherein saidN-hydroxyurea silver halide developing agent is represented by theformula:

0 R NH ii NH on wherein R is phenyl, p-methylphenyl, p-

methoxyphenyl or p-chlorophenyl.

3. The photographic processing composition of claim 1 also comprising a3-pyrazolidone silver halide developing agent.

4. A photographic silver halide developer solution comprising analkaline development activator, a l-phenyl-3-pyrazolidone silver halidedeveloping agent and an N-hydroxyurea silver halide developing agentrepresented by the formula:

wherein R is phenyl, p-methylphenyl, methoxyphenyl or p-chlorophenyl. 4:

1. A photographic processing composition comprising an alkalinedevelopment activator and an N-hydroxyurea silver halide developingagent, said N-hydroxyurea silver halide developing agent beingrepresented by the formula:
 1. A PHOTOGRAPHIC PROCESSING COMPOSITIONCOMPRISING AN ALKALINE DEVELOPMENT ACTIVATOR AND AN N-HYDROXYUREA SILVERHALIDE DEVELOPING AGENT, SAID N-HYDROXYUREA SILVER HALIDE DEVELOPINGAGENT BEING REPRESENTED BY THE FORMULA: R1-N(-R2)-CO-N(-R3)-OH WHEREINR1 IS HYDROGEN, ALKYL CONTAINING 1 TO 4 CARBON ATOMS OR ARYL CONTAINING6 TO 10 CARBON ATOMS; R2 IS HYDROGEN, ALKYL CONTAINING 1 TO 4 CARBONATOMS OR ARYL CONTAINING 6 TO 10 CARBON ATOMS; R3 IS HYDROGEN, ALKYLCONTAINING 1 TO 4 CARBON ATOMS OR ARYL CONTAINING 6 TO 10 CARBON ATOMS.2. The photographic processing composition of claim 1 wherein said 3.The photographic processing composition of claim 1 also comprising a3-pyrazolidone silver halide developing agent.